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## About
This is a Lisp written in C. It follows the outline in this [Build Your Own Lisp](https://buildyourownlisp.com/chapter11_variables) book, though it then adds some small tweaks and improvements and quality of life improvements:
This is a Lisp written in C. It follows the outline in this [Build Your Own Lisp](https://buildyourownlisp.com) book, though it then adds tweaks and quality of life improvements:
- A makefile
- Configurable verbosity levels
@ -57,38 +57,54 @@ Simply call the `./mumble` binary:
```
mumble> (1 2 3)
mumble> { 1 2 3 }
mumble> head (1 2 3)
mumble> { head (1 2 3) }
mumble> head {1 2 3}
mumble> { head {1 2 3) }
mumble> tail { 1 2 3 }
mumble> list ( 1 2 3 )
mumble> eval { head {1 2 3} }
mumble> (eval { head {+ tail head } } ) 1 2 3
mumble> len {1 2 3}
mumble> join { {1 2} {3 4} }
mumble> def { {x} { 100 } }
mumble> x
mumble> def { { a b c } { 1 2 3} }
mumble> * a b c
mumble> - a b c
mumble> / a b c
mumble> VERBOSITY=0
mumble> VERBOSITY=1
mumble> def {x} { 100 }
mumble> def {y} 100
mumble> (x y)
mumble> VERBOSITY=2
mumble> def {sq} (@ {x} {* x x})
mumble> sq 44
mumble> VERBOSITY=1
mumble> def {sqsum} (@ {x y} {(+ (sq x) (sq y))})
mumble> sqsum 2 3
mumble> VERBOSITY=0
mumble> def {init} (@ {xs} { list((head xs)) } )
mumble> def {kopf} (@ {xx} { head (list xx) } )
mumble> init {1 2}
mumble> kopf (1 2)
mumble> ifelse 1 2 3
mumble> if 1 2 3
mumble> ifelse 0 1 2
mumble> if 0 1 2
mumble> if {1 2 3} (1) (1)
mumble> def {positive} (@ {x} {> x 0})
mumble> def {fibtest} (@ {x} {if (> x 0) {+ x 1} 0 })
mumble> fibtest 2
mumble> def {fibonacci} (@ {x} {if (> x 1) { + (fibonacci (- x 2)) ( fibonacci ( - x 1 ) ) } 1} )
mumble> fibonacci 4
mumble> def {!} (@ {x} { if ( > 1 x) 1 { * x (! (- x 1)) } })
mumble> ! 100
mumble> def {++} (@ {x} { if ( > 1 x) 0 { + x (++ (- x 1)) } })
mumble> ++ 10
mumble> def {++2} (@ {x} { / (* x (+ x 1)) 2 })
mumble> ++2 10
```
## To do
- [x] Define functions
- [x] Define if, = and >
- [x] Build fibonacci function
- [x] Build factorial function
## Gotchas
This doesn't currently run on Windows. But it easily could, with [preprocessor statements from the book].
## Usage and licensing
I don't expect this project to be such that people might want to use it. If you want a
But for the eventuality, this code is licensed under the MIT license; see the license.txt file.
This doesn't currently run on Windows. But it easily could, with the preprocessor staments from parsing.c [here](https://buildyourownlisp.com/chapter6_parsing).

BIN
mumble

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@ -1,3 +1,4 @@
https://buildyourownlisp.com/chapter7_evaluation#trees
https://buildyourownlisp.com/chapter9_s_expressions
https://buildyourownlisp.com/chapter12_functions
https://buildyourownlisp.com/chapter13_conditionals

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@ -782,7 +782,6 @@ lispval* builtin_join(lispval* l, lispenv* e)
// Define a variable
lispval* builtin_def(lispval* v, lispenv* env)
{
// Takes one argument: def { { a b } { 1 2 } }
// Takes two arguments: argument: def {a} 1; def {init} (@ {x y} {x})
lispval* symbol_wrapper = v->cell[0];
lispval* value = v->cell[1];
@ -834,6 +833,77 @@ lispval* builtin_define_lambda(lispval* v, lispenv* env)
lispval* lambda = lispval_lambda_func(variables, manipulation, new_env);
return lambda;
}
// Conditionals
lispval* builtin_ifelse(lispval* v, lispenv* e)
{
// ifelse 1 {a} b
LISPVAL_ASSERT(v->count == 3, "Error: function ifelse passed too many arguments. Try ifelse choice result alternative, e.g., if (1 (a) {b})");
lispval* choice = v->cell[0];
lispval* result = v->cell[1];
lispval* alternative = v->cell[2];
if( choice->type == LISPVAL_NUM && choice->num == 0){
lispval* answer = clone_lispval(alternative);
if(answer->type == LISPVAL_QEXPR){
answer->type = LISPVAL_SEXPR;
answer = evaluate_lispval(answer, e);
}
return answer;
}else {
lispval* answer = clone_lispval(result);
if(answer->type == LISPVAL_QEXPR){
// answer = builtin_eval(answer, e);
answer->type = LISPVAL_SEXPR;
answer = evaluate_lispval(answer, e);
}
return answer;
}
}
// Comparators: =, > (also potentially <, >=, <=, <=)
// For numbers.
lispval* builtin_equal(lispval* v, lispenv* e)
{
// ifelse 1 {a} b
LISPVAL_ASSERT(v->count == 2, "Error: function = takes two numeric arguments. Try (= 1 2)");
lispval* a = v->cell[0];
lispval* b = v->cell[1];
LISPVAL_ASSERT(a->type == LISPVAL_NUM, "Error: Functio = only takes numeric arguments.");
LISPVAL_ASSERT(b->type == LISPVAL_NUM, "Error: Functio = only takes numeric arguments.");
if(a->num == b->num){
return lispval_num(1);
}else {
return lispval_num(0);
}
}
lispval* builtin_greater_than(lispval* v, lispenv* e)
{
// ifelse 1 {a} b
LISPVAL_ASSERT(v->count == 2, "Error: function = takes two numeric arguments. Try (= 1 2)");
lispval* a = v->cell[0];
lispval* b = v->cell[1];
LISPVAL_ASSERT(a->type == LISPVAL_NUM, "Error: Functio = only takes numeric arguments.");
LISPVAL_ASSERT(b->type == LISPVAL_NUM, "Error: Functio = only takes numeric arguments.");
if(a->num > b->num){
return lispval_num(1);
}else {
return lispval_num(0);
}
}
// Simple math ops
lispval* builtin_math_ops(char* op, lispval* v, lispenv* e)
{
@ -931,8 +1001,13 @@ void lispenv_add_builtins(lispenv* env)
lispenv_add_builtin("tail", builtin_tail, env);
lispenv_add_builtin("eval", builtin_eval, env);
lispenv_add_builtin("join", builtin_join, env);
lispenv_add_builtin("len", builtin_len, env);
lispenv_add_builtin("def", builtin_def, env);
lispenv_add_builtin("@", builtin_define_lambda, env);
lispenv_add_builtin("ifelse", builtin_ifelse, env);
lispenv_add_builtin("if", builtin_ifelse, env);
lispenv_add_builtin("=", builtin_equal, env);
lispenv_add_builtin(">", builtin_greater_than, env);
}
// Evaluate the lispval