{"id":3236,"date":"2016-06-26T17:01:31","date_gmt":"2016-06-26T16:01:31","guid":{"rendered":"https:\/\/stevepedwards.today\/DebianAdmin\/?p=3236"},"modified":"2016-06-26T17:01:31","modified_gmt":"2016-06-26T16:01:31","slug":"practical-c-programming-switch-and-nested-switches-example","status":"publish","type":"post","link":"https:\/\/stevepedwards.today\/DebianAdmin\/practical-c-programming-switch-and-nested-switches-example\/","title":{"rendered":"Practical C Programming – Switch and Nested Switches Example"},"content":{"rendered":"
<\/div>\n

<\/path><\/svg><\/i> \"Loading\"<\/p>\n

<\/div>\n

I wanted to explore a further level of switching to implement a sub level menu within a main switch option, by adding to my Imperial to metric units converter. This allows extra functionality to a handy program - a two way units conversion choice. \u00a0<\/span><\/p>\n

Although trial and error placement is slow, it does let you think more about a program's operation, so help the learning curve, rather than just google an answer. The first working version program code is:<\/span><\/p>\n

\/*units converter for dist, vol or mass*\/<\/span>
\n#include <stdio.h><\/span>
\nfloat km; \/*= 1;*\/<\/span>
\nfloat miles; \/*= 1.60934 * km ;*\/<\/span>
\nfloat litre; \/*= 1;*\/<\/span>
\nfloat pints; \/*= (1.75975 \/ litre);*\/<\/span>
\nfloat gallons; \/*= (8 * pints);*\/<\/span>
\nfloat kg; \/*= 1;*\/<\/span>
\nfloat lb; \/* = (2.204622 * kg);*\/<\/span>
\nchar line[10]; \/*input value array space *\/<\/span>
\nchar operator; \/* menu operator the user specified *\/<\/span>
\nfloat value; \/* input value the user specified *\/<\/span>
\nfloat result;<\/span>
\nint main()<\/span>
\n{<\/span>
\nwhile (1)<\/span>
\n {<\/span>
\n printf(\"program to convert Imperial units to metric. Enter menu option: \\n\");<\/span>
\n printf(\"1: km to miles\\n\");<\/span>
\n printf(\"2: litres to pints\\n\");<\/span>
\n printf(\"3: kg to pounds\\n\");<\/span>
\n printf(\"q: quit\\n\");<\/span>
\n fgets(line, sizeof(line), stdin);<\/span>
\n sscanf(line, \"%c\", &operator);<\/span><\/p>\n

if ((operator == 'q') || (operator == 'Q'))<\/span>
\n break;<\/span>
\n switch (operator)<\/span>
\n {<\/span>
\n case '1':<\/span>
\n printf(\"1: convert km to miles. Enter km value: \");<\/span>
\n fgets(line, sizeof(line), stdin);<\/span>
\n sscanf(line, \"%f\", &value);<\/span>
\n result = value \/ 1.60934;<\/span>
\n printf(\"%f km is %0.3f miles \\n\\n\", value, result);<\/span>
\n break;<\/span><\/p>\n

case '2':<\/span>
\n printf(\"1: convert litres to pints. Enter litre value: \");<\/span>
\n fgets(line, sizeof(line), stdin);<\/span>
\n sscanf(line, \"%f\", &value);<\/span>
\n result = value * 1.75975;<\/span>
\n gallons = result\/8;<\/span>
\n printf(\"%0.3f litres is %0.3f pints or %0.3f gallons\\n\\n\", value, result, gallons );<\/span>
\n break;<\/span><\/p>\n

case '3':<\/span>
\n printf(\"3: convert kg to pounds. Enter kg value: \");<\/span>
\n fgets(line, sizeof(line), stdin);<\/span>
\n sscanf(line, \"%f\", &value);<\/span>
\n result = value * 2.204622;<\/span>
\n printf(\"%0.3f kg is %0.3f pounds \\n\\n\", value, result);<\/span>
\n break;<\/span><\/p>\n

default:<\/span>
\n {<\/span>
\n printf(\"Invalid key, try again! %c\\n\\n\", operator);<\/span>
\n break;<\/span>
\n }<\/span>
\n }<\/span>
\n }<\/span>
\nprintf(\"\\n\"); \/*tidy cmd line*\/<\/span>
\nreturn (0);<\/span>
\n}<\/span><\/p>\n

\"unitconverter.png\"<\/a><\/p>\n

This offers only metric to Imperial units conversion at present:<\/p>\n

$ .\/unitsconverter<\/span>
\nprogram to convert Imperial units to metric. Enter menu option: <\/span>
\n1: km to miles<\/span>
\n2: litres to pints<\/span>
\n3: kg to pounds<\/span>
\nq: quit<\/span>
\n1<\/span>
\n1: convert km to miles. Enter km value: 1<\/span>
\n1.000000 km is 0.621 miles<\/span><\/p>\n

program to convert Imperial units to metric. Enter menu option: <\/span>
\n1: km to miles<\/span>
\n2: litres to pints<\/span>
\n3: kg to pounds<\/span>
\nq: quit<\/span>
\nw<\/span>
\nInvalid key, try again! w<\/span><\/p>\n

program to convert Imperial units to metric. Enter menu option: <\/span>
\n1: km to miles<\/span>
\n2: litres to pints<\/span>
\n3: kg to pounds<\/span>
\nq: quit<\/span>
\nq<\/span><\/p>\n

Now it was just finding the correct format using clues from the above switch cases - with breaks in the right places - to make the extra nested switch options behave as desired. The first working case 1 sub menu code is shown below so you can see how it enters the first case option and breaks out to the main menu after either choice is completed:<\/p>\n

int main()<\/span>
\n{<\/span>
\nwhile (1)<\/span>
\n {<\/span>
\n printf(\"program to convert Imperial units to metric. Enter menu option: \\n\");<\/span>
\n printf(\"1: km to miles\\n\");<\/span>
\n printf(\"2: litres to pints\\n\");<\/span>
\n printf(\"3: kg to pounds\\n\");<\/span>
\n printf(\"q: quit\\n\");<\/span>
\n fgets(line, sizeof(line), stdin);<\/span>
\n sscanf(line, \"%c\", &operator);<\/span><\/p>\n

if ((operator == 'q') || (operator == 'Q'))<\/span>
\n break;<\/span>
\n switch (operator)<\/span>
\n {<\/span>
\n case '1':<\/span>
\n printf(\"Want to (k) convert km to miles or (m) miles to km?: \");<\/span>
\n fgets(line, sizeof(line), stdin);<\/span>
\n sscanf(line, \"%c\", &operator);<\/span>
\n switch (operator)<\/span>
\n {<\/span>
\n case 'k':<\/span>
\n printf(\"k: convert km to miles. Enter km value: \");<\/span>
\n fgets(line, sizeof(line), stdin);<\/span>
\n sscanf(line, \"%f\", &value);<\/span>
\n result = value \/ 1.60934;<\/span>
\n printf(\"%f km is %0.3f miles \\n\\n\", value, result);<\/span>
\n break;<\/span>
\n case 'm':<\/span>
\n printf(\"m: convert miles to km. Enter miles value: \");<\/span>
\n fgets(line, sizeof(line), stdin);<\/span>
\n sscanf(line, \"%f\", &value);<\/span>
\n result = value * 1.60934;<\/span>
\n printf(\"%f m is %0.3f km \\n\\n\", value, result);<\/span>
\n break;<\/span>
\n }<\/span>
\n break;<\/span>
\n case '2':<\/span>
\n printf(\"2: convert litres to pints. Enter litre value: \");<\/span>
\n fgets(line, sizeof(line), stdin);<\/span>
\n sscanf(line, \"%f\", &value);<\/span>
\n result = value * 1.75975;<\/span>
\n gallons = result\/8;<\/span>
\n printf(\"%0.3f litres is %0.3f pints or %0.3f gallons\\n\\n\", value, result, gallons );<\/span>
\n break;<\/span><\/p>\n

This shows both extra options working as required:<\/p>\n

$ .\/unitsconverter2<\/span>
\nprogram to convert Imperial units to metric. Enter menu option: <\/span>
\n1: km to miles<\/span>
\n2: litres to pints<\/span>
\n3: kg to pounds<\/span>
\nq: quit<\/span>
\n1<\/span>
\nWant to (k) convert km to miles or (m) miles to km?: k<\/span>
\nk: convert km to miles. Enter km value: 1<\/span>
\n1.000000 km is 0.621 miles<\/span><\/p>\n

program to convert Imperial units to metric. Enter menu option: <\/span>
\n1: km to miles<\/span>
\n2: litres to pints<\/span>
\n3: kg to pounds<\/span>
\nq: quit<\/span>
\n1<\/span>
\nWant to (k) convert km to miles or (m) miles to km?: m<\/span>
\nm: convert miles to km. Enter miles value: 1<\/span>
\n1.000000 m is 1.609 km<\/span><\/p>\n

program to convert Imperial units to metric. Enter menu option: <\/span>
\n1: km to miles<\/span>
\n2: litres to pints<\/span>
\n3: kg to pounds<\/span>
\nq: quit<\/span>
\nInvalid key, try again! w<\/span><\/p>\n

program to convert Imperial units to metric. Enter menu option: <\/span>
\n1: km to miles<\/span>
\n2: litres to pints<\/span>
\n3: kg to pounds<\/span>
\nq: quit<\/span>
\nq<\/span><\/p>\n

\"unitsconv2.c.png\"<\/a><\/p>\n

Now it's just a case of pasting the same format to the other 2 options and re-arranging the formulae and units.<\/p>\n

The exit beaks from the final main case 3 have to be correctly placed with {}'s to account for the default already in place:<\/p>\n

\"case3conv.png\"<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

<\/div>\n

<\/path><\/svg><\/i> \"Loading\"<\/p>\n

<\/div>\n

I wanted to explore a further level of switching to implement a sub level menu within a main switch option, by adding to my Imperial to metric units converter. This allows extra functionality to a handy program - a two way units conversion choice. \u00a0 Although trial and error placement is slow, it does let ...\u00a0 Practical C Programming – Switch and Nested Switches Example<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[],"class_list":["post-3236","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"a3_pvc":{"activated":true,"total_views":1,"today_views":0},"_links":{"self":[{"href":"https:\/\/stevepedwards.today\/DebianAdmin\/wp-json\/wp\/v2\/posts\/3236","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/stevepedwards.today\/DebianAdmin\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/stevepedwards.today\/DebianAdmin\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/stevepedwards.today\/DebianAdmin\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/stevepedwards.today\/DebianAdmin\/wp-json\/wp\/v2\/comments?post=3236"}],"version-history":[{"count":0,"href":"https:\/\/stevepedwards.today\/DebianAdmin\/wp-json\/wp\/v2\/posts\/3236\/revisions"}],"wp:attachment":[{"href":"https:\/\/stevepedwards.today\/DebianAdmin\/wp-json\/wp\/v2\/media?parent=3236"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/stevepedwards.today\/DebianAdmin\/wp-json\/wp\/v2\/categories?post=3236"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/stevepedwards.today\/DebianAdmin\/wp-json\/wp\/v2\/tags?post=3236"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}