Formatting & Display

CalcMark offers several formatting and display features for rates, dates, napkin-math estimates, precise values, capacity planning, multiplier suffixes, and percentages.

Rates and the over keyword #

Rate Literals #

Create rates using the slash syntax:

net_bandwidth = 100 MB/s
salary = $120000/year
load = 1000 req/s

Rate Accumulation with over #

Use over to calculate the total from a rate over time:

link_speed = 100 MB/s
daily_transfer = link_speed over 1 day

hourly_rate = $75/hour
daily_earnings = hourly_rate over 8 hours

Rate Conversion #

Convert rates to different time units using convert_rate():

convert_rate(1000 req/s, minute)    -> 60000 req/min
convert_rate($120000/year, month)   -> $10000/month

Rate Arithmetic Widening #

When you multiply or divide by a rate (rate on the right), CalcMark drops the time denominator and uses the rate’s amount. This is called widening – the rate widens into a plain quantity.

When the rate is on the left side, it stays a rate. This lets you scale rates naturally with rate * number.

posts_rate = 2 posts/week
scaled = posts_rate * 3           -> 6 posts/week  (rate * number → rate)
total  = 3 * posts_rate           -> 6 posts       (number * rate → quantity)

The rule is simple: left operand wins. If you start with a rate, you get a rate. If you start with a number or quantity and multiply by a rate, you get a number or quantity.

See the Language Reference: Rate Arithmetic Widening for the full type dispatch table.

Date Arithmetic #

Date Literals #

project_start = Jan 15 2025
christmas = Dec 25 2025
now = today

CalcMark recognizes today, tomorrow, and yesterday as date keywords.

Duration Arithmetic #

project_start = Jan 15 2025
duration = 12 weeks
project_end = project_start + duration

deadline = Jun 1 2025
launch = deadline - 2 weeks

The from Keyword #

7 days from Jan 1 2025   -> Wednesday, January 8, 2025
2 weeks from today       -> (today + 14 days)

Napkin Math #

The as napkin modifier rounds results to 2 significant figures and normalizes units. It adds a ~ prefix to signal the result is an approximation.

Syntax: expression as napkin

Works with: Number, Quantity, Currency, Duration, Rate

432000 MB as napkin                 -> ~420 GB
100 MB/s over 30 days as napkin    -> ~248 TB
$1234567 as napkin                  -> ~$1.2M

This is useful for quick back-of-the-envelope calculations where exact precision is not needed.

Precise Display #

The as precise modifier is the opposite of as napkin. It shows full float precision, skipping all display rounding. This is useful when you need exact values from unit conversions.

Syntax: expression as precise

10 meters as feet                  -> 32.8 feet
10 meters as feet as precise       -> 32.808399 feet

Explicit unit conversions are rounded by default for readability. Use as precise when you need the exact value.

Capacity Planning #

Use the at...per syntax to calculate how many units you need:

disks = 10 TB at 2 TB per disk
servers = 10000 req/s at 450 req/s per server
servers_buffered = 10000 req/s at 450 req/s per server with 20% buffer

Multiplier Suffixes #

Use K, M, B for large numbers:

users = 10M
revenue = $5B
requests = 100K

Percentages #

Percentages work naturally in calculations:

price = $100
discount = 20%
sale_price = price * (1 - discount)

tax_rate = 8.25%
tax = price * tax_rate