regex for matching numeric values
#ALL THESE REQUIRE THE WHOLE STRING TO BE A NUMBER
#For numbers embedded in sentences, see discussion below
#### NUMBERS AND DECIMALS ONLY ####
#No commas allowed
#Pass: (1000.0), (001), (.001)
#Fail: (1,000.0)
^\d*\.?\d+$
#No commas allowed
#Can't start with "."
#Pass: (0.01)
#Fail: (.01)
^(\d+\.)?\d+$
#### CURRENCY ####
#No commas allowed
#"$" optional
#Can't start with "."
#Either 0 or 2 decimal digits
#Pass: ($1000), (1.00), ($0.11)
#Fail: ($1.0), (1.), ($1.000), ($.11)
^\$?\d+(\.\d{2})?$
#### COMMA-GROUPED ####
#Commas required between powers of 1,000
#Can't start with "."
#Pass: (1,000,000), (0.001)
#Fail: (1000000), (1,00,00,00), (.001)
^\d{1,3}(,\d{3})*(\.\d+)?$
#Commas required
#Cannot be empty
#Pass: (1,000.100), (.001)
#Fail: (1000), ()
^(?=.)(\d{1,3}(,\d{3})*)?(\.\d+)?$
#Commas optional as long as they're consistent
#Can't start with "."
#Pass: (1,000,000), (1000000)
#Fail: (10000,000), (1,00,00)
^(\d+|\d{1,3}(,\d{3})*)(\.\d+)?$
#### LEADING AND TRAILING ZEROES ####
#No commas allowed
#Can't start with "."
#No leading zeroes in integer part
#Pass: (1.00), (0.00)
#Fail: (001)
^([1-9]\d*|0)(\.\d+)?$
#No commas allowed
#Can't start with "."
#No trailing zeroes in decimal part
#Pass: (1), (0.1)
#Fail: (1.00), (0.1000)
^\d+(\.\d*[1-9])?$