[Shell: math constructs] #bash #math #double #parenthesis #(( #sh #seq #bc #range

math.sh

##### `((` (DOUBLE PARENTHESIS) #####
# Bash only
# arithmetic expansion
(( a=25 )) # C style setting
(( a++ )) && echo $a # a == 26; same as `(( ++a ))`
(( a-- )) && echo $a # a == 25; same as `(( --a ))`
# arithmetic evaluation
(( t = a<45?7:11 )) # t == 7; if a < 45, then t = 7, else t = 11
# https://www.tldp.org/LDP/abs/html/loops1.html#FORLOOPC
LIMIT=10
for ((a=1; a <= LIMIT ; a++)) # `for ((a=1, b=1; a <= LIMIT ; a++, b++))`
do
  echo -n "$a " # `echo -n "$a-$b "`
done

##### seq (SEQUENCE) #####
# https://www.tldp.org/LDP/abs/html/loops1.html#FORLOOPC
seq 10 # sequence 1 to 10
seq -10 0 # sequence -10 to 0

##### `{<#>..<#>}` (BRACE EXPANSION W/ RANGE) #####
# https://www.tldp.org/LDP/abs/html/loops1.html#FORLOOPC
echo {1..10} # list 1-10

##### bc (BASIC CALCULATOR) #####
# -l: math library (mathlib)
# -i: interactive
# scale: allows setting scale (precision/decimal places)
# s: sine
# c: cosine
# a: arctangent
# l: natural logarithm
# e: exponential
pi=$(echo "scale=10; 4*a(1)" | bc -l)