Below is a function which allows the user to enter an arithmetic expression and then evaluate it and return the result.\u00a0 This will work for addition (+), subtraction(-), multiplication(*), division(\/), and exponentiation(^).\u00a0\u00a0 You can also enter parenthesis to change the order of precedence if needed.\u00a0 You would call this from where ever you like to validate and convert user entered expressions.<\/p>\n
Example:\u00a0 you need to calculate the area of a circle the user types in.\u00a0 User would type “3.14*8^2” in the case of a circle with a radius of 8.\u00a0 Function would return a string of “200.96”<\/p>\n
public function string uf_eval_arithmetic_expression (string infix_expr, integer precision);\n\n\/\/ convert an expression into a numeric value (string in, number converted to string out)\n\/\/\ndecimal ld_result, ld_operand_stack [], ld_operand1, ld_operand2, ld_temp_result\nstring ls_infix_str, ls_currchar\nstring ls_infix_token [], ls_operator_stack [], ls_postfix_token [], ls_token\ninteger li_stack_top, li_itoken_sub, li_ptoken_sub\ninteger li_incoming_priority, li_instack_priority\nchar lc_temp_char\nstring ls_temp_string\nld_result = 0\n\/\/********************************************************************\n\/\/ first check the syntax of the infix arithmetic expression and put\n\/\/ each token into the ls_infix_token array\n\/\/********************************************************************\nls_infix_str = lefttrim (infix_expr) + "@"\nls_currchar = left (ls_infix_str, 1)\nls_token = ""\nDO WHILE 1 = 1\n CHOOSE CASE ls_currchar\n CASE "@"\n exit\n CASE "^", "*", "\/", "+", "-", "(", ")"\n li_itoken_sub = li_itoken_sub + 1\n ls_infix_token [li_itoken_sub] = ls_currchar\n ls_infix_str = lefttrim (mid (ls_infix_str, 2))\n ls_currchar = left (ls_infix_str, 1)\n CASE '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '.'\n DO WHILE 1 = 1\n ls_token = ls_token + ls_currchar\n ls_infix_str = Mid(ls_infix_str, 2)\n lc_temp_char = Left(ls_infix_str, 1)\n ls_temp_string = Mid(ls_infix_str, 2, 1)\n IF lc_temp_char = " " AND IsNumber(ls_temp_string) THEN\n ls_token = " "\n Exit\n END IF\n ls_infix_str = LeftTrim(ls_infix_str)\n ls_currchar = left (ls_infix_str, 1)\n CHOOSE CASE ls_currchar\n CASE "@", "^", "*", "\/", "+", "-", "(", ")"\n exit\n END CHOOSE\n LOOP\n IF isnumber (ls_token) THEN\n li_itoken_sub = li_itoken_sub + 1\n ls_infix_token [li_itoken_sub] = ls_token\n ls_token = ""\n ELSE\n \/\/messagebox ("uf_eval_arithmetic_expression ", "invalid number")\n return (infix_expr)\n END IF\n IF ls_currchar = "@" THEN\n exit\n END IF\n CASE ELSE\n \/\/messagebox ("uf_eval_arithmetic_expression ", "invalid expression")\n return (infix_expr)\n END CHOOSE\nLOOP\n\/\/********************************************************************\n\/\/ second convert the infix expression into postfix notation\n\/\/********************************************************************\nls_infix_token [li_itoken_sub + 1] = "@"\nli_stack_top = 0\nli_itoken_sub = 0\nli_ptoken_sub = 0\nDO WHILE 1 = 1\n li_itoken_sub = li_itoken_sub + 1\n ls_token = ls_infix_token [li_itoken_sub]\n CHOOSE CASE ls_token\n CASE "@"\n DO WHILE li_stack_top > 0\n li_ptoken_sub = li_ptoken_sub + 1\n ls_postfix_token [li_ptoken_sub] = ls_operator_stack [li_stack_top]\n li_stack_top = li_stack_top - 1\n LOOP\n exit\n CASE ")"\n DO WHILE ls_operator_stack [li_stack_top] <> "("\n li_ptoken_sub = li_ptoken_sub + 1\n ls_postfix_token [li_ptoken_sub] = ls_operator_stack [li_stack_top]\n li_stack_top = li_stack_top - 1\n LOOP\n li_stack_top = li_stack_top - 1\n CASE "^", "*", "\/", "+", "-", "("\n DO WHILE 1 = 1\n CHOOSE CASE ls_token\n CASE "+", "-"\n li_incoming_priority = 1\n CASE "*", "\/"\n li_incoming_priority = 2\n CASE ELSE\n li_incoming_priority = 4\n END CHOOSE\n IF li_stack_top = 0 THEN\n li_instack_priority = 0\n ELSE\n CHOOSE CASE ls_operator_stack [li_stack_top]\n CASE "+", "-"\n li_instack_priority = 1\n CASE "*", "\/"\n li_instack_priority = 2\n CASE "^"\n li_instack_priority = 3\n CASE ELSE\n li_instack_priority = 0\n END CHOOSE\n END IF\n IF li_incoming_priority > li_instack_priority THEN\n exit\n END IF\n li_ptoken_sub = li_ptoken_sub + 1\n ls_postfix_token [li_ptoken_sub] = ls_operator_stack [li_stack_top]\n li_stack_top = li_stack_top - 1\n LOOP\n li_stack_top = li_stack_top + 1\n ls_operator_stack [li_stack_top] = ls_token\n CASE ELSE\u00a0 \/* ls_token is an operand *\/\n li_ptoken_sub = li_ptoken_sub + 1\n ls_postfix_token [li_ptoken_sub] = ls_token\n END CHOOSE\nLOOP\n\/\/********************************************************************\n\/\/ third evaluate the postfix arithmetic expression. each token is\n\/\/ stored as a string occurance in the ls_postfix_token array\n\/\/********************************************************************\nls_postfix_token [li_ptoken_sub + 1] = "@"\nld_result = 0\nli_stack_top = 0\nli_ptoken_sub = 0\nDO WHILE 1 = 1\n li_ptoken_sub = li_ptoken_sub + 1\n ls_token = ls_postfix_token [li_ptoken_sub]\n CHOOSE CASE ls_token\n CASE "@"\n IF li_stack_top = 0 THEN\n return ""\n END IF\n ld_result = round (ld_operand_stack [li_stack_top], precision)\n return (string(ld_result, "0.####"))\n CASE "^", "*", "\/", "+", "-"\n IF ls_token = "\/" and ld_operand_stack [li_stack_top] = 0 THEN\n \/\/messagebox ("fx_eval_arith_expr", "divide by zero error")\n return (infix_expr)\n END IF\n IF li_stack_top < 2 THEN\n \/\/messagebox ("uf_eval_arithmetic_expression ", "invalid expression")\n return (infix_expr)\n END IF\n ld_operand1 = ld_operand_stack [li_stack_top - 1]\n ld_operand2 = ld_operand_stack [li_stack_top]\n CHOOSE CASE ls_token\n CASE "+"\n ld_temp_result = ld_operand1 + ld_operand2\n CASE "-"\n ld_temp_result = ld_operand1 - ld_operand2\n CASE "*"\n ld_temp_result = ld_operand1 * ld_operand2\n CASE "\/"\n ld_temp_result = ld_operand1 \/ ld_operand2\n CASE ELSE\n ld_temp_result = ld_operand1 ^ ld_operand2\n END CHOOSE\n ld_operand_stack [li_stack_top - 1] = ld_temp_result\n li_stack_top = li_stack_top - 1\n CASE ELSE\u00a0 \/* have an operand so add to stack *\/\n li_stack_top = li_stack_top + 1\n ld_operand_stack [li_stack_top] = dec (ls_token)\n END CHOOSE\nLOOP<\/pre>\n\n\nUpdated March 2021<\/p>\n","protected":false},"excerpt":{"rendered":"
Below is a function which allows the user to enter an arithmetic expression and then evaluate it and return the result.\u00a0 This will work for addition (+), subtraction(-), multiplication(*), division(\/), and exponentiation(^).\u00a0\u00a0 You can also enter parenthesis to change the order of precedence if needed.\u00a0 You would call this from where ever you like to…<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[3,10],"tags":[12,16],"_links":{"self":[{"href":"https:\/\/anvil-of-time.com\/wp-json\/wp\/v2\/posts\/29"}],"collection":[{"href":"https:\/\/anvil-of-time.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/anvil-of-time.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/anvil-of-time.com\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/anvil-of-time.com\/wp-json\/wp\/v2\/comments?post=29"}],"version-history":[{"count":11,"href":"https:\/\/anvil-of-time.com\/wp-json\/wp\/v2\/posts\/29\/revisions"}],"predecessor-version":[{"id":1728,"href":"https:\/\/anvil-of-time.com\/wp-json\/wp\/v2\/posts\/29\/revisions\/1728"}],"wp:attachment":[{"href":"https:\/\/anvil-of-time.com\/wp-json\/wp\/v2\/media?parent=29"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/anvil-of-time.com\/wp-json\/wp\/v2\/categories?post=29"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/anvil-of-time.com\/wp-json\/wp\/v2\/tags?post=29"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}