c ignore

Author: asyncze

c/_ignore/_hello-c.c

@@ -0,0 +1,20 @@
+// 2020-11
+#include <stdio.h>
+
+int main(int argc, char *argv[]) {
+    // filename
+    printf("filename: %s\n", argv[0]);
+    // arguments
+    if (argc > 1) {
+        printf("%s\n", "argv: ");
+        for (int i = 1; i < argc; i++) {
+            printf("\t%s\n", argv[i]);
+        }
+    }
+}
+
+// $ gcc hello-c.c -o _hello ; ./_hello
+// filename: ./_hello
+
+// $ gcc hello-c.c -o _hello-c.s -S -O0 -masm=intel -fno-stack-protector; cat _hello-c.s
+// <asm>

c/_ignore/_hello-c.s

@@ -0,0 +1,69 @@
+	.section	__TEXT,__text,regular,pure_instructions
+	.build_version macos, 13, 0	sdk_version 13, 3
+	.intel_syntax noprefix
+	.globl	_main                           ## -- Begin function main
+	.p2align	4, 0x90
+_main:                                  ## @main
+	.cfi_startproc
+## %bb.0:
+	push	rbp
+	.cfi_def_cfa_offset 16
+	.cfi_offset rbp, -16
+	mov	rbp, rsp
+	.cfi_def_cfa_register rbp
+	sub	rsp, 32
+	mov	dword ptr [rbp - 4], 0
+	mov	dword ptr [rbp - 8], edi
+	mov	qword ptr [rbp - 16], rsi
+	mov	rax, qword ptr [rbp - 16]
+	mov	rsi, qword ptr [rax]
+	lea	rdi, [rip + L_.str]
+	mov	al, 0
+	call	_printf
+	cmp	dword ptr [rbp - 8], 1
+	jle	LBB0_6
+## %bb.1:
+	lea	rdi, [rip + L_.str.1]
+	lea	rsi, [rip + L_.str.2]
+	mov	al, 0
+	call	_printf
+	mov	dword ptr [rbp - 20], 1
+LBB0_2:                                 ## =>This Inner Loop Header: Depth=1
+	mov	eax, dword ptr [rbp - 20]
+	cmp	eax, dword ptr [rbp - 8]
+	jge	LBB0_5
+## %bb.3:                               ##   in Loop: Header=BB0_2 Depth=1
+	mov	rax, qword ptr [rbp - 16]
+	movsxd	rcx, dword ptr [rbp - 20]
+	mov	rsi, qword ptr [rax + 8*rcx]
+	lea	rdi, [rip + L_.str.3]
+	mov	al, 0
+	call	_printf
+## %bb.4:                               ##   in Loop: Header=BB0_2 Depth=1
+	mov	eax, dword ptr [rbp - 20]
+	add	eax, 1
+	mov	dword ptr [rbp - 20], eax
+	jmp	LBB0_2
+LBB0_5:
+	jmp	LBB0_6
+LBB0_6:
+	xor	eax, eax
+	add	rsp, 32
+	pop	rbp
+	ret
+	.cfi_endproc
+                                        ## -- End function
+	.section	__TEXT,__cstring,cstring_literals
+L_.str:                                 ## @.str
+	.asciz	"filename: %s\n"
+
+L_.str.1:                               ## @.str.1
+	.asciz	"%s\n"
+
+L_.str.2:                               ## @.str.2
+	.asciz	"argv: "
+
+L_.str.3:                               ## @.str.3
+	.asciz	"\t%s\n"
+
+.subsections_via_symbols

c/_ignore/_other/square-root-checker.c

@@ -0,0 +1,18 @@
+#include <stdio.h>
+#include <math.h>
+
+int main(void) {
+    int base;
+
+    scanf("%d", &base);
+    if (base > 1) {
+        printf("%.8f\n", sqrt(base));
+
+    } else {
+        printf("%s\n", "Invalid base.");
+    }
+}
+
+// ./main
+// 2
+// 1.41421356

c/_ignore/_other/temperature-converter.c

@@ -0,0 +1,35 @@
+#include <stdio.h>
+#include <assert.h>
+
+// declare functions
+double c_to_f(double temp);
+double f_to_c(double temp);
+
+int main(void) {
+    double temp;
+    char unit;
+
+    scanf("%lf %c", &temp, &unit);
+    if (unit == 'C') {
+        printf("%.1f F", c_to_f(temp));
+
+    } else if (unit == 'F') {
+        printf("%.1f C", f_to_c(temp));
+    }
+}
+
+// define functions
+
+// convert C to F
+double c_to_f(double temp) {
+    return ((9.0 / 5) * temp + 32);
+}
+
+// convert F to C
+double f_to_c(double temp) {
+    return ((5.0 / 9) * (temp - 32));
+}
+
+// ./main
+// 40 C
+// 104.0 F

c/_ignore/_primer/_header.h

@@ -0,0 +1,6 @@
+#ifndef FILENAME_H
+#define FILENAME_H
+    
+const int number = 10;
+
+#endif

c/_ignore/_primer/_test.txt

@@ -0,0 +1 @@
+This is a string.

c/_ignore/_primer/arrays.c

@@ -0,0 +1,31 @@
+// 2019-08
+#include <stdio.h>
+
+int main() {
+    // array of doubles
+    double doubles[] = { 200.0, -2.2, 1.0, 0.0 };
+    printf("%f\n", doubles[1]);
+    // -2.200000
+    
+    // arrays are mutable
+    doubles[1] = 42;
+    printf("%f\n", doubles[1]);
+    // 42.000000
+    
+    // array of arrays of char with max size 10 (strings)
+    char strings[][10] = { "first", "second" };
+    printf("%s\n", strings[1]);
+    // second
+
+    // nd-array of ints
+    int matrix[2][10] = {
+        { 0, 1, 2, 3, 4 },
+        { 5, 6, 7, 8, 9 }
+    };
+    printf("%d\n", matrix[1][2]);
+    // 7
+
+    // calculate length based on type (in bytes)
+    printf("%lu\n", sizeof(doubles) / sizeof(double));
+    // 4
+}

c/_ignore/_primer/conditionals.c

@@ -0,0 +1,24 @@
+// 2019-08
+#include <stdio.h>
+
+#define ANSWER 42
+
+int main() {
+    int value = 42;
+
+    if (value < 1) {
+        // no
+    } else if (value == 1) {
+        // no
+    } else if (value == ANSWER) {
+        // yes!
+        printf("%d is the answer: %d\n", value, ANSWER);
+    } else {
+        // no
+    }
+    // 42 is the answer: 42
+
+    // single line
+    printf("%s\n", (value != ANSWER) ? "no" : "this is the answer");
+    // this is the answer
+}

c/_ignore/_primer/consts.c

@@ -0,0 +1,21 @@
+// 2019-08
+#include <stdio.h>
+
+// #define is a preprocessor directive (substitute text, inlining)
+#define A 100
+#define B 200
+
+int main() {
+    // const is an immutable variable
+    const int C = 300;
+    const int D = 400;
+
+    printf("%d\n", A);
+    // 100
+    printf("%d\n", B);
+    // 200
+    printf("%d\n", C);
+    // 300
+    printf("%d\n", D);
+    // 400
+}

c/_ignore/_primer/errors.c

@@ -0,0 +1,42 @@
+// 2019-08
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+
+extern int errno;
+
+int main() {
+    // pointer to file
+    FILE *file;
+    // error
+    int errnum;
+    // open file that does not exist
+    file = fopen("file_does_not_exist", "rb"); // error returns -1 or NULL
+    if (file == NULL) {
+        // store error code
+        errnum = errno;
+        
+        // print error code
+        fprintf(stderr, "error code: %d\n", errno);
+        // error code: 2
+
+        // perror to print string representation of error code
+        perror("");
+        // No such file or directory
+
+        // strerror to print pointer to string representation of error code
+        fprintf(stderr, "error opening file: %s\n", strerror(errnum));
+        // error opening file: No such file or directory
+    } else {
+        fclose(file);
+    }
+
+    // exit codes
+    if (1 == 0) {
+        // exit as failure (since something must be wrong?)
+        exit(EXIT_FAILURE);
+    } else {
+        exit(EXIT_SUCCESS);
+    }
+}

c/_ignore/_primer/files.c

@@ -0,0 +1,28 @@
+// 2019-08
+#include <stdio.h>
+
+int main() {
+    FILE *file;
+
+    // write to file
+    file = fopen("_file.txt", "w+");
+    fprintf(file, "%s\n", "Text to write to file.\n Next line.");
+    // close file
+    fclose(file);
+
+    // read file
+    file = fopen("_file.txt", "r");
+
+    char buffer[255];
+    
+    // stop read after first space
+    // note that reading a word removes it from stream
+    fscanf(file, "%s\n", buffer);
+    printf("%s\n", buffer);
+    // Text
+
+    // stop read after first newline
+    fgets(buffer, 255, (FILE*) file);
+    printf("%s\n", buffer);
+    // to write to file.
+}

c/_ignore/_primer/functions.c

@@ -0,0 +1,19 @@
+// 2019-08
+#include <stdio.h>
+
+// declare function (normally in header file)
+int power(int base, int x);
+// define function
+int power(int base, int x) {
+    int result = 1;
+    for (int i=0; i<x; i++) {
+        result *= base;
+    }
+    // success
+    return result;
+}
+
+int main() {
+    printf("%d\n", power(2, 8));
+    // 256
+}

c/_ignore/_primer/header-files.c

@@ -0,0 +1,19 @@
+// 2020-11
+#include <stdio.h>
+
+// filename.h
+/*
+    #ifndef FILENAME_H
+    #define FILENAME_H
+    
+    const int number = 10;
+
+    #endif
+*/
+
+#include "filename.h"
+
+int main() {
+    printf("%d\n", number);
+    // 10
+}

c/_ignore/_primer/logicals.c

@@ -0,0 +1,31 @@
+// 2019-08
+#include <stdio.h>
+#include <stdbool.h>
+
+int main() {
+    const bool YES = true;
+    const bool NO = false;
+
+    printf("%d\n", YES || NO);
+    // 1
+    printf("%d\n", YES && (YES && NO));
+    // 0
+    printf("%d\n", !YES);
+    // 0
+    printf("%d\n", !(!YES));
+    // 1
+
+    // equality
+    printf("%d\n", 1 == 1);
+    // 1
+    printf("%d\n", 1 != 1);
+    // 0
+    printf("%d\n", 1 > 0);
+    // 1
+    printf("%d\n", 1 < 0);
+    // 0
+    printf("%d\n", 1 >= 1);
+    // 1
+    printf("%d\n", 1 <= 0);
+    // 0
+}