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Squashed 'lispBM/lispBM/' changes from a5683c69..075fd296 

075fd296 fix bug related to pattern matching guards
02b38d42 update lbmref
fb312618 update lbmref
884a0973 update lbmref
32af7455 update lbmref

git-subtree-dir: lispBM/lispBM
git-subtree-split: 075fd296a8c6061ae8c5a45b017392700675b1d8
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Benjamin Vedder 2022-11-10 12:08:00 +01:00
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189
doc/lbmref.md
View File

@ -1,18 +1,19 @@
# LispBM language reference
## About Symbols
## About Symbols
Symbols are very important and fundamental to LispBM and also perhaps
a bit different from identifiers/names used in languages such as C, so
a short intro could be good here.
Symbols are very important and fundamental to LispBM and also perhaps
a bit different from identifiers/names used in languages such as C, so
a short intro could be good here.
A symbol can be thought of as a name and can be used to give names
to functions or values (variables). A symbol can also be treated and
used as a value in and of itself a value (or data). So it can be used
to name data and functions and is itself also data.
A symbol can be thought of as a name and can be used to give names
to functions or values (variables). A symbol can also be treated and
used as a value in and of itself a value (or data). So it can be used
to name data and functions and is itself also data.
---
**NOTE**
---
**NOTE**
Symbols are expressed as strings in your program such as `a`, `let`,
`define`, `+` or `orange`. The "reader", the part of LBM that parses
@ -23,18 +24,18 @@ identifier you want to print. So the runtime system is never wasting
time comparing strings to see if a symbol is this or that symbol, it's
all integer comparisons.
---
---
You associate values with symbols using, <a href="#define">define</a>,
<a href="#let">let</a> and you can change the value bound to a "variable"
<a href="#let">let</a> and you can change the value bound to a "variable"
using <a href="#setvar">setvar</a>
Not all symbols are treated the same in LBM. Some symbols are treated as
Not all symbols are treated the same in LBM. Some symbols are treated as
special because of their very fundamental nature. Among these special symbols
you find `define`, `let` and `lambda` for example. These are things that you
should not be able to redefine and trying to redefine them leads to an error.
There are two classes of symbols that are special by naming convention and
these either start with a `#`, for fast-lookup variables, and `ext-` for
you find `define`, `let` and `lambda` for example. These are things that you
should not be able to redefine and trying to redefine them leads to an error.
There are two classes of symbols that are special by naming convention and
these either start with a `#`, for fast-lookup variables, and `ext-` for
extensions that will be bound at runtime.
Examples of symbols used as data are `nil` and `t`. `nil` is used the
@ -162,7 +163,7 @@ expression evaluates to `t`.
### not-eq
`not-eq` implements the negation of eq. In other words, `(not-eq a b c)` evaluates
to the same result as `(not (eq a b c))`.
to the same result as `(not (eq a b c))`.
---
@ -220,7 +221,7 @@ Example
---
### >=
### >=
Greater than or equal comparison. A less than comparison has the form `(>= expr1 ... exprN)`
and evaluates to `t` if expr1 is greater than or equal to all of expr2 ... exprN.
@ -571,7 +572,7 @@ The conditions are checked from first to last and for the first `cond-exprN`
that evaluates to true, the corresponding `exprN` is evaluated.
If no `cond-exprN` evaluates to true, the result of the entire conditional
is `nil`.
is `nil`.
Example that prints "Hello world":
```clj
@ -818,7 +819,7 @@ cons cells on the heap.
A cons cell can be used to store a pair of values. You create a pair by
sticking a value in both the car and cdr field of a cons cell using either `'(1 . 2)` or
`(cons 1 2)`.
`(cons 1 2)`.
![pair](images/pair.png?raw=true "pair")
@ -1045,28 +1046,28 @@ Now change the value in the cdr field of apa to 42.
```
The `apa` pair is now `(1 . 42)`.
## Associations lists (alists)
## Associations lists (alists)
Association lists (alists) are, just like regular lists, built out
of cons-cells. The difference is that an alist is a list of pairs
where the first element in each par can be thought of as a key and
Association lists (alists) are, just like regular lists, built out
of cons-cells. The difference is that an alist is a list of pairs
where the first element in each par can be thought of as a key and
the second element can be thought of as the value. So alists implement
a key-value lookup structure.
a key-value lookup structure.
`(list '(1 . horse) '(2 . donkey) '(3 . shark))` is an example
of an alist with integer keys and symbol values.
`(list '(1 . horse) '(2 . donkey) '(3 . shark))` is an example
of an alist with integer keys and symbol values.
### acons
### acons
The `acons` form is similar to `cons`, it attaches one more element
onto an alist. The element that is added consists of a key and a value
so `acons` takes one more argument than `cons`. The form of an
`acons` expression is `(acons key-expr val-expr alist-expr)`.
The `alist-expr` should evaluate to an alist but there are no checks
to ensure this.
The `acons` form is similar to `cons`, it attaches one more element
onto an alist. The element that is added consists of a key and a value
so `acons` takes one more argument than `cons`. The form of an
`acons` expression is `(acons key-expr val-expr alist-expr)`.
The `alist-expr` should evaluate to an alist but there are no checks
to ensure this.
Example that adds the key `4` and associated value `lemur` to
an existing alist.
Example that adds the key `4` and associated value `lemur` to
an existing alist.
```clj
# (acons 4 'lemur (list '(1 . horse) '(2 . donkey) '(3 . shark)))
@ -1112,31 +1113,31 @@ alist. The form of a `setassoc` expression is `(setassoc alist-expr key-expr val
### array-create
Create an array of a given type, default is an array of bytes. The
Create an array of a given type, default is an array of bytes. The
form of an `array-create` expression is either `(array-create type size-expr)`
or `(array-create size-expr)`. If no type is specified, the default is
to create an array of bytes.
or `(array-create size-expr)`. If no type is specified, the default is
to create an array of bytes.
Currently the following types can be used for the type field:
| Type |
| --- |
| type-char |
| type-byte |
| Type |
| --- |
| type-char |
| type-byte |
| type-i32 |
| type-u32 |
| type-u32 |
| type-float |
| type-i64 |
| type-i64 |
| type-u64 |
| type-double |
| type-double |
---
### array-size
Returns the size of an array in number of elements. The form
of an `array-size` expression is `(array-size arr-expr)` where
arr-expr has to evaluate into an array.
Returns the size of an array in number of elements. The form
of an `array-size` expression is `(array-size arr-expr)` where
arr-expr has to evaluate into an array.
---
@ -1186,27 +1187,27 @@ Example:
### Array literal syntax
Array literals can be created using the `[` and `]` syntax to enclose
Array literals can be created using the `[` and `]` syntax to enclose
values to initialize the array with. The `[` and `]` syntax is complete
resolved in the parser and thus cannot contain arbitrary lisp terms.
the values listed between the `[` and the `]` must be literals!
resolved in the parser and thus cannot contain arbitrary lisp terms.
the values listed between the `[` and the `]` must be literals!
The form of the `[` and `]` syntax is `[ type-qualifier val1 ... valN ]`
or `[ val1 ... valN]`. If no type-qualifier is specified the default is
to create an array with byte values.
or `[ val1 ... valN]`. If no type-qualifier is specified the default is
to create an array with byte values.
The currently valid type qualifiers are:
| Type qualifier |
| --- |
| Type qualifier |
| --- |
| type-byte |
| type-i32 |
| type-u32 |
| type-float |
| type-i32 |
| type-u32 |
| type-float |
(The rest of the numerical types will be supported in the future)
(The rest of the numerical types will be supported in the future)
Example that creates a byte array
Example that creates a byte array
```clj
[ 1 2 3 4 5 6 7 8 9 10 ]
```
@ -1238,6 +1239,15 @@ For example the match expression below evaluates to 2.
---
### no_match
The `no_match` symbol is returned from pattern matching if
no case matches the expression.
- Add a catch-all case to your pattern-matching. `_`.
---
### _
The underscore pattern matches anything.
@ -1506,21 +1516,30 @@ Below is an example that conditionally returns.
---
## Unparsable symbols
## Error handling
Unparsable symbols cannot be written into a program. The unparsable symbols
signals different kinds of error conditions that may point at something
being wrong in the code (or that it is exhausting all resources).
If an error occurs while evaluating a program, the process that runs
that program is killed. The result of the killed process is set to an
error symbol indicating what went wrong.
### no_match
If the process was created using `spawn` (or equivalently, started by a
issuing a command in the repl), the process dies and an error message
is presented over the registered printing callback (dependent on how LispBM
is integrated into your system). The `ctx_done_callback` is also called
and performs other integration dependent tasks related to the shutting down
of a process.
The `no_match` symbol is returned from pattern matching if
no case matches the expression.
- Add a catch-all case to your pattern-matching. `_`.
If the process was created using `spawn-trap`, in addition to the
above, a message is sent to the parent process (the process that
executed the spawn-trap) containing information about the process that
struck an error. See <a href="#spawn-trap">spawn-trap</a>.
The parent process can now choose to restart the process that crashed
or to take some other action.
---
## Error Symbols
### read_error
The `read_error` symbol is returned if the reader cannot
@ -1558,7 +1577,7 @@ but semantically nonsensical.
### out_of_memory
The `out_of_memory` symbol is returned if the heap is full and running
the garbage collector was not able to free any memory up.
the garbage collector was not able to free any memory up.
The program you have written requires more memory.
@ -1669,61 +1688,61 @@ A value with type `type-u` occupy 28bits on the 32 bit version of LBM and
---
### type-stream
### type-channel
---
## Type convertion functions
## Type convertion functions
### to-byte
Convert any numerical value to a byte.
Convert any numerical value to a byte.
If the input is not a number the output of this function will be 0.
---
### to-i
Convert a value of any numerical type to an integer.
Convert a value of any numerical type to an integer.
The resulting integer is a 28bit value on 32bit platforms and 56 bits on 64 bit platforms.
If the input is not a number the output of this function will be 0.
---
---
### to-u
### to-u
Convert a value of any numerical type to an unsigned integer.
Convert a value of any numerical type to an unsigned integer.
The resulting integer is a 28bit value on 32bit platforms and 56 bits on 64 bit platforms.
If the input is not a number the output of this function will be 0.
---
---
### to-i32
Convert any numerical value to a 32bit int.
If the input is not a number the output of this function will be 0.
---
---
### to-u32
### to-u32
Convert any numerical value to a 32bit unsigned int.
---
---
### to-float
Convert any numerical value to a single precision floating point value.
If the input is not a number the output of this function will be 0.
---
---
### to-i64
Convert any numerical value to a 64bit int.
If the input is not a number the output of this function will be 0.
---
---
### to-u64

1
include/lbm_version.h
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@ -34,6 +34,7 @@ extern "C" {
/*! \page changelog Changelog
Nov 9: Version 0.7.1
- Bugfix: string literal lengths.
- not-eq and != added.
- Corrected behaviour for eval when applied to no argument.
- lbm_memory operations are protected by mutex.

10
src/eval_cps.c
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@ -2246,7 +2246,7 @@ static void cont_match(eval_context_t *ctx) {
if (match(pattern, e, &new_env, &do_gc)) {
if (check_guard) {
CHECK_STACK(lbm_push_3(&ctx->K, lbm_cdr(patterns), ctx->curr_env, MATCH));
CHECK_STACK(lbm_push_3(&ctx->K, body, e, MATCH_GUARD));
CHECK_STACK(lbm_push_4(&ctx->K, new_env, body, e, MATCH_GUARD));
ctx->curr_env = new_env;
ctx->curr_exp = n1; // The guard
} else {
@ -2267,7 +2267,7 @@ static void cont_match(eval_context_t *ctx) {
}
if (check_guard) {
CHECK_STACK(lbm_push_3(&ctx->K, lbm_cdr(patterns), ctx->curr_env, MATCH));
CHECK_STACK(lbm_push_3(&ctx->K, body, e, MATCH_GUARD));
CHECK_STACK(lbm_push_4(&ctx->K, new_env, body, e, MATCH_GUARD));
ctx->curr_env = new_env;
ctx->curr_exp = n1; // The guard
} else {
@ -2354,14 +2354,16 @@ static void cont_match_guard(eval_context_t *ctx) {
if (lbm_is_symbol_nil(ctx->r)) {
lbm_value e;
lbm_pop(&ctx->K, &e);
lbm_stack_drop(&ctx->K, 1);
lbm_stack_drop(&ctx->K, 2);
ctx->r = e;
ctx->app_cont = true;
} else {
lbm_value body;
lbm_value env;
lbm_stack_drop(&ctx->K, 1);
lbm_pop(&ctx->K, &body);
lbm_pop_2(&ctx->K, &body, &env);
lbm_stack_drop(&ctx->K, 3);
ctx->curr_env = env;
ctx->curr_exp = body;
}
}

9
tests/test_match_guard_6.lisp Normal file
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@ -0,0 +1,9 @@
(defun f (x)
(match x
( (? x) (< x 5) 'smaller)
( (? x) (> x 5) 'larger)
( _ 'whatever)))
(and (eq (f 23) 'larger)
(eq (f 0.3) 'smaller))

9
tests/test_match_guard_7.lisp Normal file
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@ -0,0 +1,9 @@
(defun f (x)
(match x
( (? x) (< x 5) (list x 'smaller))
( (? x) (> x 5) (list x 'larger))
( _ 'whatever)))
(and (eq (f 23) '(23 larger))
(eq (f 0.3) '(0.3 smaller)))