A small statically-typed language which compiles to a subset of MIPS (emulator is included).
On a linux machine, you need only
git clone https://github.com/goodpaul6/WatLang
cd WatLang
make
in order to compile the executable.
On windows, if you have visual studio, you must define the environment variable VS_CMD_LINE_BUILD_PATH to wherever your vcvarsall.bat is located. Then, you can
git clone https://github.com/goodpaul6/WatLang
cd WatLang
mkdir bin
build.bat
You can then run code by writing
wat path/to/file.wat
// This provides the procedure 'putn' which outputs a number to stdout
#include "basic.wat"
func fact(n : int) : int {
if(n < 2) return 1;
return n * fact(n - 1);
}
func main() : void {
putn(fact(5));
}
Prints 120 to stdout as required.
Let's have a look at the putn procedure definition.
func putn(n : int) : void {
// Make room on the stack for 20 digits (4 * 20 = 80 bytes)
asm "lis $3";
asm ".word 80";
asm "sub $30, $30, $3";
// We store the digit pointer in $4
asm "add $4, $30, $0";
// $5 is 10 for the first loop
asm "lis $5";
asm ".word 10";
asm "putnstart:";
asm "beq $1, $0, putnprint";
asm "div $1, $5";
// Put the result of the modulo into digit memory and move the pointer
asm "mfhi $6";
asm "mflo $1";
asm "sw $6, 0($4)";
asm "lis $6";
asm ".word 4";
asm "add $4, $4, $6";
asm "lis $6";
asm ".word putnstart";
asm "jr $6";
asm "putnprint:";
asm "lis $5";
asm ".word 0xffff000c";
asm "putnprintloop:";
asm "beq $4, $30, putnend";
asm "lw $6, -4($4)";
asm "lis $7";
asm ".word 48";
asm "add $6, $6, $7";
asm "sw $6, 0($5)";
asm "lis $6";
asm ".word 4";
asm "sub $4, $4, $6";
asm "lis $6";
asm ".word putnprintloop";
asm "jr $6";
asm "putnend:";
asm "lis $3";
asm ".word 80";
asm "add $30, $30, $3";
putc(10);
}
Notice how it makes use of inline assembly to perform the operation efficiently.