From c25bc8bff130460980496593f001143c9a6d6b37 Mon Sep 17 00:00:00 2001
From: sejo <sejo@texto-plano.xyz>
Date: Thu, 2 Sep 2021 16:15:36 -0500
Subject: [PATCH] initial commit

---
 Makefile                        |  2 +
 README.md                       |  0
 machines/contador-alternado.txt |  7 +++
 machines/contador.txt           |  6 +++
 machines/parentesis.txt         | 16 ++++++
 machines/paridad.txt            | 11 ++++
 machines/test.txt               |  7 +++
 turingsim.c                     | 93 +++++++++++++++++++++++++++++++++
 8 files changed, 142 insertions(+)
 create mode 100644 Makefile
 create mode 100644 README.md
 create mode 100644 machines/contador-alternado.txt
 create mode 100644 machines/contador.txt
 create mode 100644 machines/parentesis.txt
 create mode 100644 machines/paridad.txt
 create mode 100644 machines/test.txt
 create mode 100644 turingsim.c

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..ad09d47
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,2 @@
+build:
+	cc -std=c89 -Wall turingsim.c -o turingsim
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..e69de29
diff --git a/machines/contador-alternado.txt b/machines/contador-alternado.txt
new file mode 100644
index 0000000..505adda
--- /dev/null
+++ b/machines/contador-alternado.txt
@@ -0,0 +1,7 @@
+0
+0000001
+0
+2
+00110
+10000
+80
diff --git a/machines/contador.txt b/machines/contador.txt
new file mode 100644
index 0000000..3361c65
--- /dev/null
+++ b/machines/contador.txt
@@ -0,0 +1,6 @@
+0
+0000001
+0
+1
+00010
+80
diff --git a/machines/parentesis.txt b/machines/parentesis.txt
new file mode 100644
index 0000000..49fcfcf
--- /dev/null
+++ b/machines/parentesis.txt
@@ -0,0 +1,16 @@
+a
+A(()())A
+1
+11
+a)bX1
+a(a(0
+aAcA1
+aXaX0
+b)b)1
+b(aX0
+bAH00
+bXbX1
+c(H00
+cAH10
+cXcX1
+80
\ No newline at end of file
diff --git a/machines/paridad.txt b/machines/paridad.txt
new file mode 100644
index 0000000..9170d04
--- /dev/null
+++ b/machines/paridad.txt
@@ -0,0 +1,11 @@
+a
+101100B
+0
+6
+a0a00
+a1b00
+aBH00
+b0b00
+b1a00
+bBH10
+80
\ No newline at end of file
diff --git a/machines/test.txt b/machines/test.txt
new file mode 100644
index 0000000..974d6cf
--- /dev/null
+++ b/machines/test.txt
@@ -0,0 +1,7 @@
+a
+0000001
+0
+2
+a0a10
+a1a10
+4
diff --git a/turingsim.c b/turingsim.c
new file mode 100644
index 0000000..aee9c72
--- /dev/null
+++ b/turingsim.c
@@ -0,0 +1,93 @@
+#include <stdio.h>
+
+#define TAPE_SIZE 80
+#define RULES_SIZE 256
+
+typedef struct {
+	char state; /* current state */
+	char symbol; /* current symbol */
+	int head; /* index of head */
+	char tape[TAPE_SIZE]; /* tape of characters */
+	int nrules; /* number of rules */
+	/* state, symbol, new state, new symbol, direction (even right, odd left ) */
+	char rules[RULES_SIZE][5];
+} Machine;
+
+Machine m;
+int nsteps;
+
+int main(int argc, char *argv[]){
+	int i,n=0;
+	FILE *f;
+
+	if(!(f = fopen(argv[1], "r"))){
+		fprintf(stderr, "failed to load file\n");
+		return 1;
+	}
+	printf("%s\n\n", argv[1]);
+
+	/* read machine description */
+	printf("initial state: ");
+	fscanf(f,"%c",&m.state);
+	printf("%c\n",m.state);
+
+	printf("initial tape: ");
+	fscanf(f,"%s",m.tape);
+	printf("%s\n",m.tape);
+
+	printf("initial position of head: ");
+	fscanf(f,"%d",&m.head);
+	m.head = (m.head+TAPE_SIZE)%TAPE_SIZE;
+	printf("%d\n",m.head);
+
+	printf("number of rules: ");
+	fscanf(f,"%d",&m.nrules);
+	printf("%d\n",m.nrules);
+
+	for(i=0; i<m.nrules; i++){
+		printf("rule number %d: ",i);
+		fscanf(f,"%s",m.rules[i]);
+		printf("%s\n",m.rules[i]);
+
+	}
+	printf("max number of simulation steps: ");
+	fscanf(f,"%d",&nsteps);
+	printf("%d\n\n",nsteps);
+
+	/* simulate */
+	int irules; /* rules index */
+	do{
+		printf("step %d\n",n);
+		/* print head and state */
+		for(i=0; i<m.head; i++)
+			printf(" ");
+		printf("%c\n",m.state);
+		/* print tape: */
+		printf("%s\n",m.tape);
+
+		/* get symbol at head position */
+		m.symbol = m.tape[ m.head ]; 
+
+		/* search for corresponding rule */
+		irules = -1;
+		for(i=0; i<m.nrules && irules<0; i++)
+			if(m.rules[i][0] == m.state && m.rules[i][1] == m.symbol)
+				irules = i;
+		
+		if( irules == -1) /* halt if not found */
+			printf("halted\n");
+		else{ /* update machine otherwise */
+			m.state = m.rules[irules][2]; /* new state */
+			m.tape[ m.head ] = m.rules[irules][3]; /* new symbol */
+			/* move head */
+			if( m.rules[irules][4]%2 ) /* if odd, move to left */
+				m.head = (m.head-1+TAPE_SIZE)%TAPE_SIZE;
+			else /* if even, move to right */
+				m.head = (m.head+1)%TAPE_SIZE;
+		}
+
+		printf("\n");
+	}while( ++n<nsteps && irules != -1);
+
+	return 0;
+}