vocab stuff, compare

1 files changed, 52 insertions, 0 deletions

diff --git a/sanctuary.s b/sanctuary.s
index 4108078..83b924e 100644
--- a/sanctuary.s
+++ b/sanctuary.s
@@ -1108,6 +1108,58 @@ defcode "u>=", ugreatereq, 0
 	ret
 ; }}}
 
+; todo doc
+; ( a¹ u¹ a² u² -- n )
+defcode "compare", compare, 0
+	pspop r11 ; u2
+	pspop rdi ; a2
+	pspop r13 ; u1
+	pspop rsi ; a1
+
+	; check a* = 0?
+
+.loop:
+	cmpsb
+
+	jl .below
+	jg .above
+
+	dec r11
+	dec r13
+
+	; check both = 0
+	; either of these = 0 then jmp accordingly also
+
+	cmp r11, 0
+	jne .11n0
+
+	cmp r13, 0 ; r11 = r13 & strings identical
+	je .same
+
+	; u2 > u1
+	jmp .above
+
+.11n0:
+	cmp r13, 0 ; u1 < u2
+	je .below
+
+.cont:
+	jmp .loop
+
+.below:
+	mov r11, true
+	jmp .e
+
+.above:
+	mov r11, 1
+	jmp .e
+
+.same:
+	mov r11, false
+.e:
+	pspush r11
+	ret
+
 defcode "branch", branch, 0
 	mov r12, [dp]
 	mov byte [r12], 0xe9